Dual-speed bicycle hub with centrifugally controlled gear shift



5, 19-70 H. J. SCHWERDHOFER DUAL SPEED BICYCLE HUB WlTH CENTRIFUUAIJLJYCONTROLLED GEAR SHIFT Filed May 22,1969

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United States Patent O 3,546,970 DUAL-SPEED BICYCLE HUB WITH CENTRIFU.GALLY CONTROLLED GEAR SHIFT Hans Joachim Schwerdhiifer, Schweinfurt(Main), Germany, assignor to Fichtel & Sachs A.G., Schweinfurt (Main),Germany Filed May 22, 1969, Ser. No. 826,949 Claims priority,application Germany, June 8, 1968, 1,755,682 Int. Cl. F16h 1/04, 3/02U.S. Cl. 74752 4 Claims ABSTRACT OF THE DISCLOSURE A bicycle hub havinga planetary drive transmission and two overrunning clutches whichconnect the planet carrier or the ring gear of the transmission to thehub shell is controlled by a flyweight on a support rotated by the hubshell in the same direction, but at higher speed. The clutch on the ringgear is normally disengaged by a control ring connected to the ring gearby a friction coupling. A similar coupling connects a shifting sleeve tothe hub shell. The sleeve and ring are threadedly connected so that thering moves axially on the axially secured sleeve when they rotate atdifferent speeds. The sleeve is drivingly engaged by the flyweight athigh wheel speeds.

BACKGROUND OF THE INVENTION This invention relates to automaticallyshifting multiple speed hubs for the wheels of bicycles and likevehicles, and particularly to a hub having at least two speeds andcontrolled by a centrifugal governor in response to the rotary speed ofthe wheel and of the hub.

Conventional hubs of the type described have a planetary geartransmission arranged in the shell of the hub which is coaxially mountedon a shaft. The transmission is drivingly interposed between an inputwheel or chain sprocket and the hub shell and includes two transmissionmembers which are connected for rotation at different speeds, such as aplanet carrier and a ring gear, when the input wheel is turned. Twooverrunning clutches are respectively associated With the twotransmission elements and interposed between the same and the hub shellfor driving the latter at two different speeds. A centrifugal governoroperates one of the overrunning clutches for this purpose.

The governor has a flyweight mounted on a support which is rotated aboutthe hub axis by a step-up transmission connected to the hub shell topermit a reduction in the size of the flyweight. A further reduction inthe flyweight size has been made possible by a known arrangement inwhich the flyweight merely turns a shifting member, and threadedengagement between the shifting element and a control member causes thelatter to move axially in the hub to thereby disengage one of theaforementioned overruning clutches when the flyweight rotates fastenough so that centrifugal forces acting on the weight overcome therestraint of a biasing spring, and the weight moves away from its axisof rotation.

This invention aims at improving the afore-described multiple-speed hub.

SUMMARY OF THE INVENTION In the improved hub of the invention, thestep-up transmission rotates the flyweight support in the same directionas the hub shell, and the flyweight engages the shifting member forrotating the latter at the speed of the support when the flyweight movesaway from the hub axis. The shifting member is axially secured andyieldably coupled to the hub shell. The rotatable and axially movablecontrol member is yieldably coupled to the ring gear in the planetarydrive transmission, and the shifting and control members are threadedlyconnected in such a manner that the control member disengages theoverrunning clutch associated with the ring gear when the shiftingmember is rotated by its yieldable coupling at the lower speed of thehub shell, while the control member permits engagement of the lastmentioned clutch when the shifting member is driven by the flyweight ata speed which is higher than that of the ring gear.

Additional features, further objects, and many of the attendantadvantages of this invention will readily become apparent from thefollowing detailed description of a preferred embodiment when consideredin connection with the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTReferring now to the drawing in detail, and initially to FIGS. 1 and 2,there is seen a rear wheel hub for a bicycle whose shaft 1 is normallyfixedly fastened to the bicycle frame. A planet carrier 2 rotatablysupported on the shaft 1 is integral with a sprocket 3 normally drivenby a chain on the right side of the bicycle and carries planet gears 4on respective shafts 31, only one of the three planet gears being shown.The planet carrier 2 also carries two diametrically opposite pawls 5which are held in engagement with a rim of ratchet teeth 6 on the hubshell 7 by a pawl spring, not shown in FIGS. 1 and 2 and conventional initself. The hub shell 2 rotates about the axis of the shaft 1 on ballbearings 8, 9, the ball bearing 8 being interposed between the shell 7and the planet carrier 2.

The planet gears 4 simultaneously mesh with a sun gear 10 fixed on theshaft 1 and with a ring gear 11 so as to turn the latter about the axisof the shaft 1 at a speed higher than the input speed of the hub, thatis, the speed of the sprocket 3 on the planet carrier 2. Rotation may betransmitted from the ring gear 11 to the hub shell 7 by means of pawls12 on the ring gear 11 which are spring-biased toward engagement with aratchet 28 on the hub shell 7. Engagement between the pawls 12 and theratchet 28 is prevented in the low-gear condition of FIG. 1, andpermitted in the high-gear condition of FIG. 2 by a control ring 13.

The control ring 13 is coupled to the ring gear 11 by a friction spring14 which is coiled about a cylindrical face of the ring gear and has afree end 33 which radially projects from the cylindrical face of thering gear into an axial groove 34 in an inner face of the ring 13, as isbest seen in FIG. 4. External, coarse, left-handed threads 15 on thering 13 engage corresponding inner threads of a shifting sleeve 16 whichis yieldably coupled to the hub shell 7 by a leaf spring 17 attached tothe sleeve and frictionally engaging the hub shell. A frustoconical face18 on the control ring 13 engages the pawls 12 in the axial ringposition illustrated in FIG. 1 to pivot the pawls away from the ratchet28, and the pawls are engaged with the ratchet by an associated,nonillustrated pawl spring, when the control ring 13 moves on thethreads 15 away from the pawls 12 into the position of FIG. 2.

In the position of the control ring 13 shown in FIG. 1, the hub shell 7is turned by the pawls at the same rotary speed as the input sprocket 3.In the position of the control ring illustrated in FIG. 2, the hub shell7 is rotated at the higher speed of the ring gear 11 by the pawls 12,and the ratchet teeth 6 overtravel the pawls 5.

The control ring 13 is shifted axially between the two illustratedpositions by a centrifugal governor driven by the hub shell 7 throughepicyclic step-up gearing. An internal gear rim 19 on the hub shell 7drives intermediate meshing gears 21, 21a. A bearing member which isfixed on the shaft 1 and carries the afore-mentioned ball bearing 9 alsosupports the shafts 22, 22a of the intermediate gears 21, 21a, the gear21 meshing with the gear rim 19 and the gear 21a, and the latter meshingwith the central gear 23 of the step-up gearing.

The central gear 23 is fixed on a tubular support 24 which rotates onthe shaft 1 and carries a fiyweight 25 pivotally mounted on the support24 so as to swing away from the shaft 1 at a wheel speed sufficient toovercome the restraint of a return spring 27. In its operative positionremote from the shaft 1, the fiyweight 25 engages an abutment 26 on theshifting sleeve 16. The sleeve is normally taken along by the spring 17at the speed of the hub 7, but turns faster when the fiyweight 25engages the abutment 26.

Axial movement of the sleeve 16 toward the drive end of the hub near thesprocket 3 is prevented by abutting engagement of a washer 37 on theaxially fixed fiyweight support 24 and of a spring ring 38 on the sleeve16.

An actual embodiment of the hub of FIGS. 1 and 2 is shown in FIGS. 3 to5. Minor structural details have been simplified in FIGS. 1 and 2 forconvenient pictorial representation. The hub illustrated in FIGS. 3 to 5thus is as described above except as explicitly stated otherwisehereinbelow.

It would not be practical to assemble a hub in which the input sprocketis integral with the planet carrier of the planetary transmission in thehub shell. The actual sprocket 3 is fixedly mounted on a tubular driver30 which rotates on the shaft 1 and is connected to a separate planetcarrier 2' by interengaged radial projections and recesses 29.

The annular outer race member 32 of the ball bearing 8 is threadedlyinserted in the shell 7 and integrally carries the sprocket teeth 6engaged by the pawls 5.

The fiyweight 25' is radially slidable in the cavity 36 of a plastichousing 24, as is best seen in FIG. 5. The housing 24' is rotatablymounted on the shaft 1 and is the functional and structural equivalentof the aforedescribed fiyweight support 24. It is integral with thecentral gear 23. The helical compression spring 27' which normally holdsthe weight 25 near the shaft 1 in the housing 24 is interposed betweenthe weight 25' and a circumferential outer wall of the housing 24'. Thefiat, circular washer 37 is axially movable on the housing 24' betweenthe axial end of the wall 35 and the spring ring 38 on the sleeve 16.

The split spring ring 38 is a piece of spring wire bent into a generallycircular shape from which four integral lugs or lobes project in aradially outward direction. The lugs or lobes are arcuate sections ofthe wire having a much smaller radius of curvature than the ring as awhole. The ring 38 is fastened to the sleeve 16 by engagement of thelugs or lobes with openings 40 in the sleeve.

The mass of the single fiyweight 25' is balanced by two cylindricalmetal rods 43 fixedly arranged in axial bores 42 in the portion of thehousing 24a which is diametrically opposite the cavity 36. The housing24a which supports the fiyweight 25' is axially fixed on the shaft 1 bya washer 44 and a snap ring 45. The washer is wide enough to retain thefiyweight 25' in the cavity 36 which is open in an axial directiontoward the sprocket 3. The end of the fiyweight 25' near the washer 44axially pro- 4 jects beyond the wall 35 of the housing 24' and has aradially outwardly directed cam-shaped projection 41.

The hub is automatically shifted between the low-speed position of FIGS.1 and 3-5 and the high-speed position of FIG. 2 in the following manner.

As long as the nonillustrated wheel rim and the hub shell 7 rotate at arelatively low speed at which centrifugal forces acting on the fiyweight25 cannot overcome the restraint of the spring 27', the pawls 12 aredisengaged by the control ring 13. The ring is rotated at the high speedof the ring gear 11 by the friction spring 14, and the shifting sleeve16 is turned by the spring 17 at the slower speed of the hub 7 in such adirection that the ring 13, if it was initially positioned otherwise, ismoved toward the right, as viewed in FIGS. 1 to 3, into the position ofFIG. 1. The pawls 12 are swung out of engagement with the ratchet 28,and the axial forces of reaction acting on the sleeve 16 are transmittedto the shaft 1 by the spring 38, the washer 37, and the housing 24. Noaxial stresses are exterted on the hub shell 7, and the rotation of thewheel is therefore not impeded by high bearing pressure.

When the pawls 12 are fully disengaged and cannot be swung further bythe ring 13, the spring 17 slips on the hub 7 or the spring 14 slips onthe cylindrical portion of the ring gear 11, wherever the friction islower.

When the wheel rotates at a speed high enough to cause radial outwardmovement of the fiyweight 25 in the housing 24, the projection 41 on thefiyweight 25 frictionally engages the shifting sleeve 16, and the sleeveis taken along at the rotary speed of the housing 24 which is higherthan that of the hub shell 7, the shell and the housing rotating in thesame direction so that the spring 17 slips on the hub shell. The rotaryspeed of the housing 24' is also higher than that of the ring gear 11and of the control ring 13 so that the ring 13 travels axially on thethreads 15 toward the left, as viewed in FIGS. 1 to 3, into the positionshown in FIG. 2. The pawls 12 are released, and the hub shell 7 isturned at the relatively high speed of the ring gear 11, thereby furtherincreasing the rotary speed of the sleeve 16 and safely holding thecontrol ring 13 in the pawl-releasing position of FIG. 2.

The fiyweight 25 reverts to the position shown in FIG. 1 when the wheelspeed drops until centrifugal forces acting on the fiyweight 25 cannotovercome the restraint of the spring 27'. The traveling speed at whichthe hub automatically shifts from low gear into high gear can be set bysuitably selecting the spring 27'. The return from high gear to low gearis not determined solely by the position of the weight 25. As long asdriving torque is transmitted from the pawls 12 to the sprocket 28, thepawls remain engaged because of the conventional sawtooth shape of thesprocket teeth, not specifically illustrated in the drawing. The hub 7thus continues rotating at the same speed as the ring gear 11, and thesleeve 16 rotates at the same speed as the control ring 13. The low-gearcondition of the hub is restored only when pedaling is momentarilyinterrupted, thereby slowing or stopping the planetary gearing so thatthe ratchet 28 on the hub shell 7 rotates faster than the pawls 12 whichare disengaged. When pedaling is resumed, the ring gear 11 rotatesfaster than the hub shell 7 and the ring 13 is shifted into the positionof FIG. 1 as described above.

The rider may thus select the moment at which the hub shifts from highinto low gear if the wheel speed is sufficiently low. Frequentunnecessary shifting back and forth between low gear and high gear isavoided, and riding comfort is improved because of the absence of theslight shock occurring when an automatic transmission of the generaltype described shifts from high gear into low gear without thecooperation of the rider.

The hub illustrated in FIGS. 3 to 5 relies for shifting into high gearon the engagement of a friction coupling between the shifting sleeve 16and the fiyweight 25, more specifically the projection 41 on thefiyweight. Under otherwise identical condition, the torque capable ofbeing transmitted by this coupling is a direct function of the mass ofthe fiyweight 25. It is essential in a bicycle hub to reduce the hubvolume to a minimum, and therefore to make the fiyweight as small aspossible.

This requirement is met in the illustrated hub in part by the fact thatthe power required for shifting is derived from the hub shell directlyand the friction coupling in the centrifugal governor merely has toovercome friction in the threads 15, the inertia of the threadedlyconnected elements 13, 16, and the friction of the spring 17 against thehub shell 7 while the sleeve 16 rotates faster than the hub shell.

In the instant invention, the hub shell 7 and the shifting sleeve 16rotate in the same direction in all operative conditions of the hubbecause of the even number of intermediate gears 21, 21a in the step-uptransmission for the housing 24' which supports the fiyweight 25'. Thespring 17 is fixedly attached to the shifting sleeve 16 and extendsobliquely in a circumferential and radial direction toward the innerwall of the hub shell 7 in such a manner that the free end of the springwhich is in contact with the shell 7 trails when the sleeve 16 turnsfaster than the hub shell 7. The spring is stressed in tension by itsfrictional engagement with the hub shell wall, and the friction betweenthe spring and the hub shell is relatively small.

When the fiyweight 25 is disengaged from the sleeve 26, torque istransmitted from the hub shell 7 to the sleeve 16 by the spring 17 whichis stressed in compression so that the contact friction between the freeend of the spring and the hub shell wall is relatively high, and muchhigher than the friction during the fast movement of the sleeve 16 whendriven by the centrifugal weight 25 by way of the friction couplingbetween the sleeve and the projection 41. The torque transmitted by thelast mentioned friction coupling during shifting into high gear is smallas compared to the torque transmitted between the hub shell 7 and thesleeve 16 when the hub is being shifted to the low-gear position.

The centrifugal governor of the invention therefore needs but a singlefiyweight 25', small enough to fit into a hub shell 7 of normaldiameter.

What is claimed is:

1. In a centrifugally controlled, automatically shifting two-speed hubfor a bicycle or like vehicle including a shaft (1) having an axis; ahub shell (7) mounted on the shaft for rotation about said axis; aninput wheel (3); a drive transmission operatively interposed betweensaid input wheel and said shell and including two transmission elements(2, 11) connected for rotation at different speeds when said input wheelis turned, and two overrunning clutches (5, 6; 12, 28) respectivelyassociated with said transmission elements and interposed between theassociated transmission elements and said shell for driving the shell attwo different speeds; and centrifugal governor means for operating oneof said overrunning clutches, the improvement in the governor meanswhich comprises:

(a) a support (24') rotatable on said shaft about said axis;

(b) step-up transmission means (19, 21, 21a, 23) interposed between saidsupport and said hub shell for rotating said support about said shaft inthe direction of rotation of the hub shell at a rotary speed higher thanthe speed of said hub shell, when the hub shell rotates about said axis;

(c) a fiyweight (25') movable on said support toward and away from saidaxis;

((1) yieldably resilient biasing means (27) biasing said fiyweighttoward said axis;

(e) a shifting member (16) rotatable about said axis;

(f) engagement means (41) on said fiyweight engageable with saidshifting member for rotating the latter at the speed of said supportwhen said fiyweight moves away from said axis against the restraint ofsaid biasing means;

(g) a control member (13) rotatable about said axis and axially movable;

(h) operating means (18) on said control member for operating said oneoverrunning clutch in response to axial movement of said control member;

(i) engaged thread means (15) on said members for moving said controlmember axially relative to said shifting member when said members rotaterelatively to each other;

(j) securing means (37, 38) axially securing said shifting member duringaxial movement of said control member;

(k) first yieldable coupling means (17) coupling said shifting member tosaid hub shell for joint rotation; and

(l) second yieldable coupling means (14) coupling said control member tothe transmission element associated with said one overrunning clutch forjoint rotation.

2. In a hub as set forth in claim 1, said drive transmission including asun gear (10) fastened to said shaft, a ring gear (11) coaxial with saidsun gear, a planet carrier (2), and a planet gear (4) rotatably mountedon said planet carrier in simultaneous meshing engagement with said sungear and said ring gear, said planet carrier and said ring gearconstituting said transmission elements, said one overrunning clutchbeing associated with said ring gear, the rotary speed of said supportbeing higher than the rotary speed of said ring gear when any one ofsaid overrunning clutches is engaged.

3. In a hub as set forth in claim 1, said securing means including means(44, 45) holding said support in an axially fixed position on saidshaft, and cooperating abutment means (37, 38) on said shifting memberand on said support.

4. In a hub as set forth in claim 3, said abutment means including aring member (38) on said shifting member and a disc member (37) on saidsupport, said shifting member being tubular, and said support beingreceived in said shifting member.

References Cited UNITED STATES PATENTS 3,143,005 8/1964 Schwerdhofer74752 3,147,641 9/1964 Schwerdhofer 74750 3,215,002 11/ 1965Schwerdhofer 74750 3,438,283 4/ 1969 Schwerdhofer 74750 3,286,549 1 1/1966 Schwerdhofer 74752 ARTHUR T. MCKEON, Primary Examiner US. Cl. X.R.74750

